Piazza, an online study network popular with college engineering students, wants to help tech startups compete in the war for talent.

A new recruiting tool called Piazza Careers lets companies connect with potential job candidates among the more than one million students who use the site. The service, which has been available for a test period to a limited group of companies, opened to everyone today, Chief Executive Pooja Sankar said in an interview.

Piazza will charge recruiters a subscription fee, starting at $20,000 per school term, to search and message candidates on the site. Similar tools are offered by professional resume site LinkedIn. But Piazza’s big advantage is its large base of top engineering students, a group that is largely absent from other job sites, said Keith Rabois, a Piazza investor who is also a former vice president at LinkedIn.

“At LinkedIn, we were never able to attract recent graduates at scale, or become the default employment platform for technical talent,” said Rabois.

Piazza’s opportunity to fill this gap enticed Rabois’ Khosla Ventures to lead an $8 million round of funding in the Palo Alto, Calif., startup which closed late last year but was not reported or announced. Rabois is also joining the board of directors.

Founded in 2009 by Sankar, Piazza lets college classmates ask and answer questions about homework and gives teachers a way to help students outside of the classroom. The company says more than half of the undergraduates at top engineering schools Stanford, Berkeley, MIT, Carnegie Mellon and Georgia Tech are on the site, with average users spending two to three hours on it each night.

Piazza’s recruiting tools could help smaller startups compete for new college grads with tech giants like Google and Facebook, who can afford to deploy large teams to college campuses each year.

“We have a small team focused on campus recruiting,” said Kenny Mendes, head of recruiting at online-storage startup Box, which began searching for potential hires and interns on Piazza in recent months. “It immediately connected us to a wide group of students,” Mendes said.

Mendes’ team uses Piazza’s search filters to narrow down its users to specific criteria, such as those who have been a teaching assistant in a computer science course, or those who have interned at Google.

He says the average quality of talent on the site is higher than elsewhere. Box recruiters might contact half of the Piazza users they review, whereas they would only reach out to as little as one-tenth of the potential job candidates they find on LinkedIn.

Piazza is still refining its service so that students on the site won’t feel inundated by company recruiters, Sankar said. For example, it may eventually limit the number of messages recruiters can send directly to students.

The new funding will also help Piazza as it aims to expand beyond math and science courses into other areas of higher education, Sankar said.